Skin is the largest and most visible organ of the human body, and is also among the tissues most exposed to environmental stresses, hazards, and pathogens. Skin is a multi-layered tissue, primarily composed of the epidermis and dermis, and includes several accessory structures, such as sweat glands, sebaceous glands, and hair follicles. Skin serves many functions. For example, it is a protective barrier to external insults (e.g., heat, chemicals, bacteria), is involved in thermoregulation, inhibits dehydration, and performs sensory functions. Skin is also a bioreactor that produces various hormones and lipids that enter the body's circulation. A variety of immune cells function in skin as a first line of defense against bacterial or viral invasion and to maintain immune surveillance in skin and nearby body tissues. For these reasons, establishment and maintenance of good skin health is important to human health.
Skin health is also important for aesthetic reasons. Many people are deeply concerned about the appearance of their skin. A healthy skin appearance is maintained by a combination of cleaning, nutrition, and application of therapeutic and cosmetic products. However, overuse of skin care products can degrade skin health and appearance. Often, individuals employ trial-and-error techniques to identify skin care products (and doses thereof) that produce a desirable skin appearance. More precise methods are needed for identifying compositions (and suitable amounts of such compositions) that will enhance the health and appearance of an individual's skin. These methods would preferably be tailored to identify useful compositions and dosages for individuals. The present invention satisfies this need.
Many skin disorders can be alleviated, inhibited, or even prevented by maintaining a high degree of skin health or by timely intervention with appropriate skin-affecting agents. For example, such intervention can include consuming or topically applying skin care products, modulating sun exposure, adjusting diet, consuming nutritional or pharmaceutical products known to be effective against skin disorders, and undergoing heightened medical monitoring. These changes are often not made, owing to the expense or inconvenience of the changes and an individual's subjective belief that he or she is not at high risk for skin disorders. Improved assessment of skin health can help to identify individuals at risk for developing skin disorders and permit more informed decisions to be made regarding whether lifestyle changes or other interventions are justified.
Many human genes occur in a variety of forms which differ in at least minor ways. Heterogeneity in human genes is believed to have arisen, in part, from minor, non-fatal mutations that have occurred in the genome over time. In some instances, differences between alternative forms of a gene are manifested as differences in the amino acid sequence of a protein encoded by the gene. Some amino acid sequence differences can alter the reactivity or substrate specificity of the protein. Differences between alternative forms of a gene can also affect the degree to which (if at all) the gene is expressed. However, many heterogeneities that occur in human genes appear not to be correlated with any particular phenotype. Known heterogeneities include, for example, single nucleotide polymorphisms (i.e., alternative forms of a gene having a difference at a single nucleotide residue). Other known polymorphic forms include those in which the sequence of larger (e.g., 2-1000 residues) portions of a gene exhibits numerous sequence differences and those which differ by the presence or absence of portion of a gene.
Numerous disorders and physiological states have been correlated with occurrence of one or more alternative forms of an individual gene in the genome of a human who exhibits the disorder or physiological state. For example, Kimura et al. (2000, Am. J. Ophthalmol. 130:769–773) discloses an association between occurrence of a SNP of the manganese superoxide dismutase gene and a form of macular degeneration.
Associations between individual disorders and individual genetic polymorphisms are known. However, disorders can usually result from polymorphisms in any of a relatively large number of genes, and as a result, assessing the polymorphic form(s) of any single gene that occur in a human's genome is usually not predictive of the likelihood that the human will develop the disorder.
A need remains for a method of assessing an individual's skin health or predisposition to develop skin disorders. Such assessment could be used to identify types and amounts of therapeutic, inhibitory, or preventive compositions or interventions that can be used to alleviate, inhibit, or prevent skin disorders. The invention satisfies these needs.